Contact spring operation and drive in automatic switch



Dec. 26, 1950 c. R. WOODLAND CONTACT SPRING OPERATION AND DRIVE IN AUTOMATIC SWITCHES Flled May 15, 1947 INVENTOR. Cecil Robert Woodland W6? ATTORNEY Patented Dec. 26, 1950 CONTACT SPRING OPERATION AND DRIVE IN AUTOMATIC SWITCH Cecil Robert Woodland, Liverpool, England, assignor to Automatic Telephone & Electric Company Limited, Liverpool, England, a British company Application May 13, 1947, Serial No. 747,781 In Great Britain May 15, 1946 8 Claims.

The present invention relates to automatic switches of the kind used in telephone or like systerns and is more particularly concerned with single motion switches known generally as uniseleotors.

In order that satisfactory automatic self interrupted operation at a speed which remains substantially constant from switch to switch and which moreover does not vary greatly from step to step on any one switch, it is advantageous to provide a late break and a late re-make of the switch interrupter contacts on the operate and release strokes of the armature respectively, and it is an object of the present invention to provide a simple and effective means of ensuring this operation of the interrupter contacts.

According to one feature of the invention the interrupter contacts are arranged so that they are under the control of the armature-actuated pawl which forms part of the pawl and ratchet mechanism which effects the stepping of the switch.

During one operate and release cycle of the armature, the pawl executes a substantially triangular movement. Thus in the well known reverse drive type of uniselector, the pawl follows the profile of the ratchet wheel tooth during the operative stroke of the armature and a substantially straight path in the root of the tooth during the restoring stroke. In the forward drive type of uniselector, the pawl follows a substantially straight path in the root of the tooth during the operative stroke and follows the profile of the tooth during the restoring stroke.

According to another feature of the invention, arrangements are provided whereby the substantially triangular movement executed by the pawl causes the interrupter contacts to remain closed during one stage of the movement, to open and remain open during another stage of the movement and to close during a further stage of the movement.

The invention will be better understood from the following description of one embodiment of the invention taken in conjunction with the accompanying drawing which shows the invention applied by way of example to a uniselector of the reverse drive type.

The uniselector which is constructed around the frame It is shown in the quiescent state with armature l3 pivoted on the knife edged member l4, and constrained in a position away from the pole face 12 of the electromagnet H by two springs It. The adjustable stop I! serves to limit the air gap between the armature and the pole face. The pawl I9 is coupled to the armature by the flat flexible spring l8 which is tensioned to cause the knife-edged tooth of the pawl to seat in the root of the teeth of the ratchet wheel 2!]. The rachet wheel is pivoted at 2|, and serves to carry wipers such as 36 which engage with bank contacts in a well-known manner.

The interrupter contacts, suitably insulated at 29, are fixed to the bracket 24 by plate 32 and screws 33. The bracket in turn is fixed to the frame by the screws 25. The lifting rod 26 is passed freely through holes at 21 and 28 in the bracket 2t and rests, under the tension of spring Bil, against the face of the pawl. The contacted spring 30 is thus held in electrical contact with spring 3!. The lifting rod 25 may be fabricated from synthetic phenol fibre board or the like or alternatively it may be of metal fitted with an insulating tip.

When the electromagnet II is energized the armature moves in the direction of the pole face l2, and the pawl tooth executes the first stage of its movement when it is caused to ride up face 22 on a tooth of the ratchet wheel. It will be noted that the movement of the pawl at this stage is therefore not vertical but substantially parallel to face Bl of the bracket and consequently the position of the rod 26 remains substantially unchanged. During this time the wheel 20 is held stationary by the flat flexible spring 34.

As the armature approaches a predetermined position towards the end of its stroke, the knifeedge of the pawl passes over the edge of the wheel tooth and under the combined pressures of springs 93 and so moves rapidly down face 23, allowing the lifting rod 26 to move axially to allow contacts 30 and 3i to open.

Following standard practice the electromagnet circuit is opened at the interrupter contacts and the armature moves away from the pole face under control of springs 5. The pawl now travels vertically downwards to step the ratchet wheel one tooth pitch and consequently the wipers move to the next contacts. The downward movement of the pawl transmits an axial movement to the rod 26 so that spring 36 re-makes with 3! at a predetermined point towards the end of the armature stroke.

It will be apparent that the invention might equally well be applied to uniselectors of the for ward stepping type, wherein, in the operate direction of the armature, the pawl moves in the root of the tooth along a substantially straight path, and in the release direction of the armature the pawl follows the profile of the tooth. In this case the lifting rod will normally be out of engagement with the contacts which will be closed and the pawl will cause axial movement of the lifting rod towards the end of the first stage of movement during which the pawl is moving in a substantially straight line in the root of the tooth. During the second stage of movement when the pawl is riding up a tooth there will be no axial movement of the rod and the contacts will remain open while the contacts will close during the third stage of movement when the pawl is moving rapidly down the other side of the tooth.

I claim:

1. An automatic selecting switch having wipers, a ratchet wheel for driving said wipers, a curved electromagnetically operated pawl, means for moving said pawl to engage the teeth of the wheel to move the same, a pair of interrupter springs and a slidable member linking the curved portion of said pawl with said springs, said: springs operated by said pawl through said slidable' member and moved thereby only near the end of the forward stroke of the pawl.

2:. In a ratchet and pawl drive fora stepping switch, a pawl, a hooked end portion on said pawl, a magnet for moving the tip of the hooked end portion of said pawl in one plane along the back of a ratchet. tooth until it falls over and engages said tooth, and means for then moving the. pawl to operate the drive, a pair of interrupter springs for the magnet, and a slidable element engaging the curved back of the hooked endportion of the pawl and said springs, said element operated. responsive to said pawl falling over said tooth for operating said springs.

3". In a ratchet and pawl drive for moving a rotary switch, a pawl, a curved hooked end on said pawl, means for moving the pawl in a first direction until the hooked end rides over the back of a tooth of the ratchet wheel, said pawl thereupon moved in a second direction into the root of the tooth, means for then moving the pawl in a third direction to drive the switch, a set of interrupter springs, a slidably mounted operating rod held in engagement with the curved hooked end of the pawl and the springs, said hooked end of said pawl when moved in said first direction, sliding along the end of the rod without causing axial movement thereof, movement of the pawl in the second direction causing axial movement of the rod to open the springs, said rod moved by the movement of the pawl in a third direction and adjusted to close said springs only as the said third movement approaches completion.

4. In an automatic selecting switch having wipers, a ratchet wheel connected to the wipers, a curvedpawl for engaging said wheel, a magnet having an armature operated thereby connected to the pawl, a pair of interrupter springs for the magnet and a slidable member connecting the curved portion of said pawl and said springs, said pawl having movement with said armature and movement relative to said armature, said springs operated at one time by the movement of the curved portion of the pawl relative to said armature.

5. ma rotary selecting switch having wipers, a ratchet wheel for driving said wipers, a pawl, a hooked end on said pawl for engaging said ratchet wheel, a bracket mounted to one side of said ratchet wheel comprising of a short and a long inclined surface, a portion of the hooked end of saidpawl being parallelly adjacent said short surface axially aligned holes in said bracket, interrupter springs mounted to the long inclined bracket surface, a rod slidably mounted within said holes and engagin said portion of the hooked end of said pawl at one end and said interrupter springs at the other end, said springs being tensioned against said rod to enable the pawl to engage a tooth of the ratchet wheel, an electromagnet having an armature pivotally attached thereto, said armature being attached to and for the purpose of driving said pawl forward causing said pawl to be guided along the radial surface of a tooth of said ratchet, said rod being maintained immovable by said pawl until said pawl reaches the vertex of said tooth and moves down the driving surface thereof, at which time said rod is freed, sliding axially, opening the interrupter springs, and means for restoring said armature thereby causing the hooked end of said attached pawl to rotate said ratchet one step and moving said slidable rod back to close said springs as the return stroke of the pawl approaches completion.

6. In a rotary selecting switch having wipers, a ratchet for driving said wipers, a pawl, a hooked end on said pawl for engaging said ratchet, a bracket mounted to one side of said ratchet wheel comprising a short and a long inclined surface, a portion of said hooked end of the pawl being parallelly adjacent said short surface axially aligned holes in said bracket, interrupter springs mounted to the long inclined bracket surface and parallel thereto, a rod slidably mounted within said holes and engaging said portion of the hooked end of said pawl at one end and said interrupter springs at the other end, an electromagnet having an armature pivotally attached thereto, a flat spring member connecting said pawl and said armature and tensioned to exert a force on said pawl to allow said pawl to engage a tooth of the ratchet, said armature and attached fiat spring cooperating for the purpose of driving said pawl forward, said pawl being guided along the radial surface of a-tooth of said ratchet, said rod being maintained immovable by said pawl until said pawl reaches the vertex of said tooth and moves down the driving surface thereof, at which time said rod is free, sliding axially, opening the interrupter springs, means for restoring said armature thereby causing the hooked end of said attached pawl to rotate said ratchet one step and moving said slidable rod back to close said springs as the return stroke of the pawl approaches completion.

7. In a rotary selecting switch as described in claim 6, wherein spring tension in said interrupter springs i against said rod cooperating with said flat spring member for causing lateral movement of said pawl to engage the next tooth on said ratchet.

8. In a rotary stepping switch having wipers, a ratchet wheel for driving said wipers, a pawl, a hooked end on said pawl for driving said ratchet wheel, an electromagnet, and armature pivotally attached thereto, said armature attachedto said pawl, a pair of contact interrupter springs, energization of said electromagnet causing the tip of the hooked end of said pawl to first move forward along the radial edge of the next tooth of said ratchet on the first leg of a triangular movement, means causing the tip of the hooked end of said pawl to slide laterally overthe driving surface of said tooth securely engaging the" same as said pawl progresses on 5 the second leg of said triangular movement, means for restoring said armature causing said attached pawl to complete the third leg of its triangular movement, thereby rotating said engaged wheel one step, and means engaging the back of the curved hooked portion of said pawl and said interrupter springs maintaining said pair of interrupter springs closed during the first movement of said; pawl, said last means operating in response to said second movement of said pawl to open said springs and said last means operating again in response to said third movement of said pawl causing said interrupter springs to close again at a predetermined point in said third movement, which point will be as the return stroke of the pawl approaches completion.

CECIL ROBERT WOODLAND.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 

